Means for controlling volume range



H. F. SHOFFSTALL MEANS FOR CONTROLLING VOLUME RANGE Nov. 9 1926.y

Filed Dec. 15, 192,4

ATTORNEY A INVENTR fJ/ma i Patented Nov. 9, 1926.

UNI-TED 'STATES PATENT'OFFICE.

HUGH F. SHOFFSTALL, OFr MAPLEWOOILNEW JERSEY, ASSIGNOR TO AMERICAN TELE. PHONE AND' TELEGRAPH COMPANY, A. CORPORATION OF NEW YORK.

MEA-Ns Fon coNTRoLLINq'voLUME RANGE.

applieatien'mea December 1a, 1924. serial No. 755,768.

mally capable of handling.

The range of volume which ordinary circuits will handle is limited principally by two factors,(1) if the volumefis allowed to fall below a certain value, noise and crosstalk interference from adjacent circuits becomes objectionable,fand (2) if the volume is permitted to increase above a Vmaximum value, cross-talk will be introduced into adjacent circuits working at a lower energy level, and also distortionwill be introduced dueto overloading of repeaters.

In connection with radio broadcasting and public address systems where the material must be transmitted toadistant point, the

range which it is desirable to transmit is considerably wider than the above conditions will permit. While it would be possible `to increase the volume range by more careful line construction andthe use of high power repeaters, the expense of this course of procedure would be prohibitive. It is proposed by the present invention to permit the transmission ot a volume range wider than that to which a given transmission circuit is limited by increasing or decreasing the volume applied to the circuit whenever it is lower or higher than the limits of the circuit, at the same time producing a complementary adjustment at the receiving end of the circuit so that the, volumel impressed upon the receiver will be the same as it would have been if no volume control whatever had tary to each other, so that if the volume isincreased at the transmitting end it will be 'decreased at the receiving end, and vice versa.

The invention will now be more fullyjunderstood from 'the following detailed .'dee scription thereof A-when readin connection with the accompanying drawing, the figure of which illustrates a of the invention.

Referring to the drawing, theapparatus at the transmitting end of the circuit is il lustrated at the left, and the corresponding apparatus at the receiving end of the circuit is illustrated at the right. ML designates the transmission line over which the energy is to be transmitted. In order to control the volume applied to the line ML, a vacuum tube amplifier A is provided having a potentiometer P whose adjustment may be preferred embodiment varied by means of a series of relays E0 to l E11, inclusive. similar vacuum tube amplifier I is interposed between the main line ML and the receiver to produce complementary adjust ments in the transmission. The gain of this amplifier is determined by a potentiometer whose setting is controlled by a'series of relays En to Elf, inclusive. The poten- At the receivin' station a' tiometer P is so arranged that as successive E relays are'operatcd from left to right the gain of the amplifier A is increased; the potentiometer P', on the other hand is so arranged that as its successive E relays are operated from left to right the gain is' decreased.

In order tocontrol the ysetting'ofthe two potentiometers, a rotatable switch S may be provided having switch arms 20 and 2l which may be madeto contact with any one of a series of contacts or segments arranged in the form of a semi-circle. If, when the arms 'A of the switch are resting upon any pair of contacts, the switch arms are moved to other contacts, impulses are transmitted over auxiliary telegraph circuits L and L. These telegraph circuits are illustrated for convenience as being separate circuits from the conductors of the main transmission line ML, but it will be understood that they may be the Morse legs obtained by compositing the line ML, or they may be phantom circuits, or any other type of telegraph circuits available in the plant.

A series of differential stepping-relays ping" relays at the two stations are arrangedY to be operated in response to the impulses transmitted from the telegraph lines tode' termine the adjustment of the potentiometers P and P', respectively, under control of the E and E. relays. Further vdetails of the invention maf now be understood from a description o the operation,I which is as follows:

Assuming that the switch S has its arms an 21 in the position shown in the drawing, that is, resting upon the 0 contacts, the circuits will be in the condition illustrated with none of the stepping relays 0perated at either station. Under these conditions relays E1, at the transmitting station and the relay E0' at the receiving station will be energized, the other E relays being deenergized so that the grid of the amplifier A 1s connected to the lowest point of the potentiometer P corresponding to the position of lowest gain ofthe amplifier. At the receiving station, however, the grid of the amplifier A will be connected lto the .highest point of the potentiometer P corresponding to the condition of maximum gain of the amplifier.

Suppose, now the switch arms 20 and21 and Y were deenergized` by reason of the short-oircuiting of their windings. The short-circuit for the relay X extends from l the terminal of its winding over the segment 22 of the switch and arm 20 to the grounded O contact. The short-circuit for the relay Y, on the other hand, extended from the terminal o its windings over thesegment 23 of the switch, arm 21,"O contact, over conductor Y... and over the lower back contact.v of relay C1. As soon as the switch arms 20` and 21 were moved from the, O contacts',

both of these ground k.connections were broken, andthe short-circuits about the windings of relays X and Y were open.

These relays are atvonce energized thereby completing a circuit from battery, `.through the winding ofy rela 24, frontcontacts .of relays X and Y ack :contact of A relay 27, and over thev ack contact of relay 26A to ground. VThe relay 24 vis energized and opens the circuit of the telegraph line L so that an open circuit impulse is `transmitted causing the release ofrelay 28 at the transmitting station and relay 28' at there-v ceiving station. y

R'lay 28, upon being delenergized, connects' ground tothe up-ccnductor 30 so` that acircuit is completed over conductor 30 and over the lower back contact of relay D1,

through vthe .lowerqwindingfof relayy Upto battery. At the same time a circuitv islcom- -pleted over the back contact of relay V28 forv the relay 26. Relay C1, upon being` ener-'pl are moved in a clockwisev position from the O contact to, say, contact No. 3 of the switch. When the switch arms rested on the O contacts, relays X ytion takes place.

' to the point 1 of the potentiometer P'. y

,sequentlv the gainV of the amplifier A at lay 26, uponl being energized, opens the circuit previously traced for the relay 24 'contacts numbered 1 of the `switch S. Rel

so that the circuit through the line L is' i I again closed and the open circuit impulse ceases. Relays 28 and 28' are energized, disconnecting ground from up-conductors 30 and30, respectively. Upon ground beingl disconnected from conductor 30, a short-circuit is removed from about the lower winding of relay- D1, and relay D1 is accordingly energized over a circuit throlgh relays C1 and 1 in series to ground over the upper front contact of relay C1. Relay D1, upon being energized, opens the normal circuit for the relay E1, at its u per back the lower windings of contact and closes the circuit o relay E1 v at its upper front contact. Relay E1, disconnects the grid of theI amplifier A from the point O of the'potentiometer'while relay E1 connects saidgrid over itsfrontI contact to the point 1 of the potentiometer P.

At the receiving station a similar opera- Upon the release of relay 28 at the beginning of the open circuit impulse, ground was connected to conductor 30 thereby energizing relay C1 through its lower windin At the end of the impulse the groun connection of conductor 20 is broken so that a circuit is established in series throu h the lower windings of relays C1 and D1 to energizel rrelay D1' and maintain both relays locked up. Relay D1 at its upper contact opens a normally energizing circuit of `relay Eo',

and closes the circuit of E1. The release of E0" disconnects the grid of the amplifier A from the O point of the potentiometer (corresponding to mairimumgain), and relay E1' at the Sametime connects said rid the sending station is increasedjoney step,

1 and the gain of the amplifier A at the kreceiving station is decreased a correspondlng step.V

At the end of the transmissid'n of the open4 circuit impulse over line L the energization Aot the relay .2S/resulted in opening the groundvconnection to the winding of relay 2 6 at `the same time that it removed the ground from the 11p-conductor 30.. Relay 26 r accordingly is released, and as the yshortcircuiting ground connections are not yet established, relays X and Y of the original circuit through the. relay 24 is again com pleted. Relay 24 now opens the circuitof.

the line' L to'transmit another open circuit impulse-through' the relays 28 and 28'." i Re.

ay 28 again connectsjground vto the up-:l's vvconductor 30. and to 'the relay 26. T he contact opens Consequently ground connection over .conductor is n ow established over the lower make contact of' relay Dl and over the lower back contact `or relay D2 and then through the lower winding of relay C2 to battery. Relay C2 upon being energized disconnects at its lower armature the ground connection over conductor Y1 and connects ground' ductors X2 and Y2. The ground iiiains connected to conductor 1 over the lower front contact of relay C1. As a result of this operation, ground is now applied to contacts l and 2 ot the upper group and to contact 2 of the lower group.

Relay 26, which was energized as a result of the beginning of the second open circuit still reimpulse again opens the circuit ot' the relay 2li which, in turn, permits its armature to fall otl and close a circuit through the line L` thus terminating the second open impulse and causing the energization of relays .28 and 28. Relay 28 disconnects ground from conductor 3() thereby removing the shortcircuit from about the lower winding o the relay D2 so that said relay is energized, over a circuit through the lower Winding oi relay CL and lower winding of relav D2 and thence over the upper C2 to ground.

Jiront contact ot' relay Both'relays are locked up over the circuit thus traced. upon being energized, at

Relay D2,

the circuit its upper Jiront ot' relay El and closes the circuit of relay ing the E2, thus connectgrid of the amplifier A to the secon oint of the potentiometer, instead ot the rst point.

At the receiving y station released y relay 28 was at the beginning of the second open circuit impulse thereby connecting ground to conductor 30 and over the'lower Jfront contact of lock-up relay l and thence over the lower back contact ot relay D2 and through the lower winding 'o relay C2 to battery. Relay C2 is accordingly energized. At the end ot' the open circuit impulse the ground connection is removed from conductor 30 thereby removing the short-circuit from the lower winding ot relay D2 so that relay D2 is energized and relays C2 and D2 are locked up over their lower windings in series with each other. Relay D2', upon being energized, opens the circuit ot relay E1 at its upper cont-.act and closes the circuit of relay E2'. rhe grid of the amplipotentiorneter P instead of to the point l. the gain of the amplifier has been decreased two steps simultaneous with the corresponding increase of the gain ot the amplifier by two steps.

Returning to the transmitting station, it will be recalled that at the end ot the secont o en circuit impulse groun was disconnected from the winding oit relay 26 so that said relay was deenergized. Short-circuitto conis now connected to point 2 ot the l thetliird point of the ing grounds are not yet connected at this time to the windings of relays X an Y and consequently the deenergization of relay 26 again completes the circuit through relay 24. The energization of relay 24 opens the circuit ot the line L thereby causing the deenergization ot relavs 28 and 28. Relay 28 again connects lip-conductor 30 so that. from 30 a circuit is established over the lower front. contacts of relays D1 an D2 and over the .lower back contact ot relay D3 and through the lower winding of relay C3 to battery. Relay C3 is energize and at its lower contact disconnects ground from conductor Y2 and connects ground to con-ductors X.q and Y3 over the connections ot succeeding relayv C4 (not shown). is now applied to contacts O, 1, the upper group andato contact 3 of the lower group ot switch S. Relays X and Y are at once short-circuited by the ground connections established over the switch arms 20 and 2l so that said relays are released. The energization ot' relay 26, in response to the initiation ot the. open circuit impulse` opens the circuit ot the relay 24 which will now remain open at the contacts of relays X andY. Relay Qlagain closes a circuit through the line L and ends the third open circuit impulse. Relays 28 and 28 are again energized, the former relay disconnecting round from relay 26 and Jfrom conductor lThe disconnection ot ground trom conductor 3() removes the short-circuit from about the lower winding of the relay D3 so that ,relays C3 and D3 are locked un in series through their lower windings.- elay D3, in turn, opens the circuit ot relay E2 an closes the circuit ot the relay E3 thereby connecting the grid ot' the amplifier to the third point ot the potentiometer Returning to relay 'll be noted Ground 6, it wi that at the end of the third open circuit impulse the said relay was again deenergized. rlflie deenergization of this relay does not again cause the energization o relay 24 by reason ot' the tact that relays X and Y are now short-circuited to maintain the circuit of said relay open. Consequently no more impulses are transmitted over the line L.

At the receiving station the relay CS was at the beginning of the. open circuit impulse when ground was connected to the rip-conductor 30. At the end ot said impulse relays C3 and D3 are locked up in series, the eiicrgization ot the latter causing the circuit of relay E2 to be opene and the circuit of E] to be closed thereby connecting the grid of the amplifier A to potentiometer. Consequently at the end ofthe third impulse the gain ot the amplifier A was increase i a third step and the gain et the amplifier Af the tel

` ings of the D re was simultaneously decreased a third step. It will therefore he clear that in response to the setting of the switch S simultaneous ceiving'ends of th words, the volume In other was increased at the transmittiiig'end and correspondingly de' creased at the receiving end.

uppose, now, with the circuits in the condition just described, the arms and 2l of the switch S clockwise direction and permitted to rest on contacts l`l of th will be energization and lock- C2 and C d said relay is energized.

heenergization of the relay a circuit lfrom ground, over the lower contact of relay 26, back contact of relay 27, front contact of relay Y, baclf Contact ot' reeenergizaot' line relay 29 connects battery to relay 27 and to the down-conductor 31. A circuit is thereby completed over conductor 31, over the innermost upper back contact of relay Dm over corresponding contacts of other counting relays (not thence over the innermost front contact of counting relay D2, through the upper Winding of said relay, and through the upper winding ot' relay 3 to ground. The Windays are aiding, but the windings of the relays are differential. Consequently the circuit just traced results Ppe? the upper winding 1s prevents the operation of h its upper winding after lwinding of relay C2.

will be recalled the circuit 'of the lower Winding has been roken. l

While these operations were taking was energized L., Relays Z9 and 2" are accordingly energized' and isconnect battery fiom t e upper conduct to cease flowing tlir windings of relay l)3 yand C3. release of relaylC3 having already opened the circuit of the lower windin'v relay 3 is accordingly deenergized thereb extending the conductor 3() to the innermost upper armature of relay D2. t its upper contact relay D3 opens the circuit of relay E3 and closes the circuit of the relay E2 thus shifting the potentiometer connection to the second point and decreasing the gain of the amplifier one step.

ace at the re eginning of the y 29 released its larmature and connected battery to the upm and over the stepping rela-ys (not shown) over the innermost upper front Contact of relay. D3', through the upper windings of relays D3 and C to ground. Relay 3 decnergized and opens 105 king circuit. through the lower winding of relay DEQ-the relay D5 b tained energized, however, through its u per winding. At its upper contact relay also connects a ground to the lead t 1e upper winding of relay D3 operation of rela-v Winding at'ter the circuit throuffh winding has heen broken.

itt the end of the open circuit impulse, line relay 29' disconnects battery from the down-conductor 31 thereby opening the cir.- cuit through the upper winding of relay D3 whici is accordingly released. Relay D3 120 contact opens the circuit E3 and closes the circuit of E2 he amvis increased one step and decreased one pl A is simultaneously step. Returning to the transmitting station, it

that at the end of the first 13G open circuit impulse relay 29 disconnected battery from the relay 27. Relay 27 is accordingly deenergized and 'again completes the circuit of relay 25 (no. short-cirouiting ground connection being yet established from the switch arm 21 for the relay Y). .Relay 25 again opens the circuit of the line L initiating a second open circuitimpulse and causing the release of the line relays 29 and 29. Battery is again Connected to relay 27 and to conductor 31 so that a circuit is now established over the innermost upper contacts of relays Dl1 and D3 and over the innermost upper front contact of relay D2 and through the upper windings of relays D, and C2 to ground. Diferential relay C2 is now released and the locking circuit through the lower winding of the relayD2 is opened, relay D2 being energized through its upper winding. Relay C2 upon being deenergized vdisconnects ground from conductors X2 and Y, and connects ground to conductor Y1 so that ground is now connected to the rst contact of the lower group ot switch S. Consequently a shortcircuit connection is established.' over the switch arm 2l `for the relay Y which is accordingly released. The relay 27 upon being energized at the beginning of the open circuit impulse opens the circuit previously traced for the relay 25. This circuit is now permanently maintained open due to the short-circuiting of the relay Y with the consequent release of the armature of said relay. Relay 25 upon being released again closes the circuit through the line L1 and energize's the relays 29 and 29. Relay 29, upon being energized, disconnects battery from the relay 27 and from conductor 31..

Relay 27, upon being released, does not again establish the circuit of relay 25 due to the deenergization of relay Y. The disconnection of battery from conductor 31 causes the release of rela D2 thereby opening the circuit of relay 2' and closing the circuit of relay A1. ri`he grid of the amplifier A is now connected to the first point of the potentiometer P.

As no further impulses are transmitted, the circuitremains in the condition thus described with all of the counting relays released except relays- C1 and D1. Ground is now connected to the contacts 0 and 1 of the upper group and to the contact l of the lower group of the switch S.

At the receivingend relay 29 is released at the beginning of-'the second open circuit impulse thereby connecting vground to' the down-conductor 31. .to release the relay C2. At the end of the open circuit impulse, relay 29' wasl again energized, disconnecting battery from the down-conductor 31 thereby releasing the relay D2. The latter relay opened the circuit of the rela E2. and closed the circuit of the relay 1 .thereby succeeding change in the setting of the' i switch S.

It will be obvious that the general principles herein disclosed maybe embodied in many other organizations widely different from those illustrated without departin from the spirit of the invention as detine in the following claims.

What is claimed is:

1. In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station, a manual control switch at one of said stations, means operated by any degree of change in the setting of said switch to transmit impulses between said stations, the number of impulses transmitted being determined by the change in the settin of said switch, and means responsive to tie transmission of said impulses to cause simultaneous and complementary adjustments of the volume at the two stations.

2. In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station, a manual control switch at one of said stations, means operated by any degree of change in the setting of said switch to transmit impulses between said stations, the number of impulses transmitted being determined by the change in the setting of said switch, and step-by-step means responsive to the transmission of said impulses to simultaneously effect complementary step-by step adjustments of the volume at the two stations. e l

In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station, a manual control switch at one of said lsta` tions, means operated by any degree of change in the setting of said switch to transmit impulses between said stations, the number of impulses transmitted being determined by the change in the setting of said switch, sets of counting relays at each station responsive to the impulses transmitted to produce simultaneously complementary step-by-step adjustments of the volume at the two stations. i p

4. In a transmission system, a transmission medium interconnecting two stations, volumeadjusting means at each station, a manual control switch at one of said stations, means `operated by any degree of change in the setting of .said switch to trans mit impulses between said stations, the numj ment of said switch in one direction and being successively operated in a reverse order in response to impulses resulting from an adjustment of said switch in the opposite direction, said counting relays producing simultaneously complementary step-by-step' adjustments of volume at the two stations. 5. In a transmission system, a transmission medium interconnecting two stations, means .for adjusting the volume at each station, al manual controlling switch at one ot said stations, a pair of auxiliary signaling circuits interconnecting said stations, means responsive to any degree of adjustment of said switch in one direction to transmit impulses over'one of said auxiliary circuits, and means responsive to any degree of adjustmenty of said switch in the opposite direction to transmit impulses over the other auxiliary circuit, the number of impulses transmitted being determined by the change in the setting of said switch, means at each station responsive to the impulses transmitted over one auxiliary circuit to produce-simultaneously an increase in volume at one station and a decrease in volume at the other station, said means responding to impulses transmitted over the other circuit to produce a decrease in the volume at the one station and an increase at the other.

6. In a transmission system, a transmission medium interconnecting two stations, means for adjusting the volume at each station, a manual controlling switch at one of said stations, a pair of auxiliary signaling circuits interconnectinggsaid stations, means responsive to any degree of adjustment of said switch in one direction to transmit impulses over one of said auxiliary circuits, and means responsive to any degree of adjustment of said switch in the opposite direction to transmit impulses over the other auxiliary circuit, the number of impulses transmitted being determined by the change in the settingr ot said switch, step-by-step means at each station for controlling the volume adjusting means, said step-by-step means being responsive to the impulses transmitted over one auxiliary circuit to ,increase the volume at one station and decrease itat the other, and said step-by-step means being responsive to impulses transmitted over the other auxiliary circuit to decrease the volume at one station and increase it at the other.

7. In a transmission system, a transmission medium' interconnecting two stations, means for adjusting the volume at each station, a manual controlling switch at one of saidstations, a pair of auxiliary signaling circuitsinterconnecting said stations, means responsive to any degree of adjustment of said switch in one direction to transmit impulses over one of said auxiliary circuits, and means responsive to any degree of adjustment of said switch in the opposite direction to transmit impulses over the other auxiliary circuit, the number of impulses transmitted being determined by the change in the setting ot' said switch, sets of counting relays at each station for controlling the volume adjusting means thereat, said counting relays operatingin response to impulses transmitted over one auxiliary circuit to increase the volume at one station and decrease it at the other and operating inresponse to impulses transmitted over the other auxiliary circuit to decrease the volume at the one station and increase it at the other.

S. In a transmission system, a transmission medium interconnecting two stations, means for adjusting the volume at each station, a manual controlling switch at one of said stations, a pair of auxiliary signaling circuits interconnecting said stations, means responsive to any degree of adjustment of said switch in one direction to transmit impulses over one of said auxiliary circuits, and means responsive to any degree of adjustment of said switch in the opposite direction to transmit impulses over the other auxiliary circuit, the number of impulses transmitted beingdetermined by the change in the setting of said switch, sets ot counting relays at each station for controlling the volume adjusting means thereat, said counting relays at lboth stations being operated successively in one order in response to impulses transmitted over the one auxiliary. circuit to increase the gain at one station and decrease itat the other, and said sets ot' counting relays being operated in the reverse order in response to impulses transmitted over the other auxiliary circuit to decrease the volume at one station and increase it at the other.

In testimony whereof, I have signed my name to this specification this 11th day ot' December, 1924.

HUGH r. sHoFrsrALL. 

